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Name and explain the… (Class 10 Science 2024, Q31)

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ScienceCBSE Class 10 · Board exam 2024, set 31/3/1 · 3 marks · Short answer

CBSE Class 10 Science 2024: question 31

Set in the CBSE Class 10 board exam of 2024, paper 31/3/1, section C, question 31, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q31 · 3 marks · Short answerThe Human Eye and the Colourful World

Name and explain the phenomenon of light due to which the path of a beam of light becomes visible when it enters a smoke filled room through a small hole. Also state the dependence of colour of the light we receive on the size of the particle of the medium through which the beam of light passes.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/3/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

The same effect makes sunlight beams visible in a dense forest.

Hint 2

Why is the clear sky blue? Relate colour to the size of the particles.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Phenomenon: Scattering of light, seen here as the Tyndall effect.

    1 mark

  2. Explanation: The smoke contains fine colloidal particles. When the beam strikes them, they scatter (diffusely reflect) light in all directions. Some of this scattered light reaches our eyes, so the path of the beam becomes visible.

    1 mark

  3. Dependence on particle size: Very fine particles scatter mainly blue light (shorter wavelengths). Larger particles scatter light of longer wavelengths. If the particles are large enough, all colours are scattered and the light appears white.

    1 mark

Answer: Tyndall effect (scattering of light). Smoke particles scatter light so the beam's path is visible. Very fine particles scatter mainly blue (short wavelength) light; larger particles scatter longer wavelengths (white if very large).

Where the marks are

  • Names scattering of light/Tyndall effect (1 mark)
  • Explains that smoke particles scatter light, making the path visible (1 mark)
  • Fine particles scatter blue/short wavelengths; larger particles scatter longer wavelengths (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from The Human Eye and the Colourful World, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 31/3/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.